[Public-List] Mainsail Foot Shelf

Tue Apr 13 11:10:44 PDT 2021

The first parts are OK, the second part is not and the third part is OK.
Rule 12.2 of The Great LAkes Aloberg Association states:
12.2. Each mainsail shall have a maximum of four (4) battens of any 
length.
Rule 11B of the Chesapeake rules state:
Each mailsail shall have 4 battens of any length.
Don

------ Original Message ------
From: "Gordon Laco via Public-List" <public-list at lists.alberg30.org>
To: "Alberg 30 Public List -- open to all" 
<public-list at lists.alberg30.org>
Cc: "Gordon Laco" <mainstay at csolve.net>
Sent: 2021-04-13 11:54:33 AM
Subject: Re: [Public-List] Mainsail Foot Shelf

>Yes, the size and shapes of all the sails are closely defined, as well as construction.  Full battens and loose footed configurations are illegal in the class.
>
>Gordon Laco
>426 Surprise
>
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>
>
>
>
>>  On Apr 13, 2021, at 11:51 AM, americo silva via Public-List <public-list at lists.alberg30.org> wrote:
>>
>>  is there a rule that states how big a main sail can be
>>
>>
>>  On Sat, Apr 10, 2021 at 2:16 PM Mike Nikolich via Public-List <
>>public-list at lists.alberg30.org> wrote:
>>
>>>
>>>
>>>  Jonathan,
>>>
>>>  I held off on writing this sooner as I thought others on this list had
>>>  previously expressed detailed views on a shelf foot and would speak up
>>>  again.  Maybe it wasn't here but on the Facebook page (and I'm rarely on
>>>  Facebook).
>>>
>>>  I would let your sailmaker determine the dimensions and shape of the
>>>  shelf.
>>>
>>>  There is nothing in the class rules that constrains it other than that the
>>>  sail must be attached to the boom for the full length of the foot and that
>>>  "no device such as zippers may be placed along the luff, the foot, and/or
>>>  the body of the sail for the purpose of adjusting the draft or the set of
>>>  the sail" (i.e. you can have a shelf foot but not one that you can zip
>>>  closed).
>>>
>>>  Without a shelf foot, the lower panels of an attached-foot mainsail are
>>>  cut flatter and flatter to provide a fair transition from the airfoil shape
>>>  of the sail to the straight line that is the foot along the boom.
>>>  For a loose-footed main the design airfoil shape is maintained all the way
>>>  down to the foot for better performance.  A sail with a shelf foot is
>>>  essentially a loose-footed main with a lightweight dacron "shelf" attached
>>>  to connect between the bottom main panel and the foot rope that still has
>>>  to be a straight line in the boom slot. The bottom line then is that the
>>>  size and shape of the shelf is driven by the shape your sailmaker has
>>>  designed into the bottom of the airfoil portion of the sail.
>>>
>>>  (There's a really bad joke somewhere in that last paragraph but I don't
>>>  know if I can find it....)
>>>
>>>  I know that my mainsail has a shelf foot but I don't know it's dimensions.
>>>  I can measure it but it will be sized based on the overall shape of the
>>>  bottom portion of my main. If considering a shelf for a new sail I would
>>>  let its dimensions be driven by your sailmaker's overall design.
>>>
>>>  Cheers!
>>>  Mike
>>>
>>>  Mike Nikolich
>>>  S/V Skybird
>>>  Alberg 30 #550
>>>mike.nikolich550 at gmail.com
>>>
>>>
>>>  On Mar 16, 2021, at 9:40 PM, Jonathan Bresler via Public-List <
>>>public-list at lists.alberg30.org> wrote:
>>>
>>>  Dear Albergers,
>>>
>>>  By class rules our mainsails must be connected to the mast and the boom.
>>>  Loose footed sails are disallowed.   One the methods for dealing with the
>>>  resulting shape
>>>  is to remove the bolt rope and  sew a half lens (half ellipse) to the foot
>>>  of the sail.
>>>  The curved side of the lens is sewn to the foot of the sail and the bolt
>>>  rope is moved
>>>  to the flat side of the lens.  This way when the outhaul is eased the
>>>  bottom portion of
>>>  the sail takes on a airfoil shape.  Then the outhaul is tight the bottom
>>>  portion of the
>>>  sail is much flatter and less powerful (better for heavy air).
>>>
>>>  How deep should the shelf be?  Wondering who has a foot shelf and what the
>>>  depth
>>>  of the shelf might be at 25%, 50%, and 75% aft along the foot.
>>>
>>>  Jonathan
>>>
>>>  --
>>>  Jonathan M Bresler
>>>  S/V Constance Alberg 30 #262
>>>  Annapolis/Eastport MD
>>>
>>>
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>
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